The description at the start of the pull request for this work-in-progress branch is worth a read for understanding the motivations behind most of the changes.

The description at the start of the pull request for this work-in-progress branch is worth a read for understanding the motivations behind most of the changes. https://github.com/twitter/bootstrap/pull/6342 https://github.com/twitter/bootstrap/pull/6342 It may also help to keep in mind that this is a preview. Bootstrap 3 isn't done yet.